1. Field of the Invention
This invention relates to an electronic part mounting apparatus for mounting electronic parts at predetermined positions of a printed circuit board, and more particularly to an apparatus for picture processing and identifying an attracted condition of an electronic part attracted to a vacuum attracting nozzle and a position of such electronic part placed on a printed circuit board.
2. Descritption of the Prior Art
In the field of automatic assembly of printed circuit boards, an electronic part mounting apparatus is employed to mount or place an electronic part such as an IC (integrated circuit) device, a small capacitor or a resistor at a predetermined position of a printed circuit board. An electronic part mounting apparatus is constituted so that two layers of a double tape in which electronic parts are accommodated are exfoliated from each other to take out an electronic part and then the thus taken out electronic part is moved to and placed at a predetermined position of a printed circuit board on which the electronic part is to be mounted.
In order to mount an electronic part accurately at a predetermined position of a printed circuit board, an accurate position of the printed circuit board must be identified, and in order to mount to electronic part accurately at the predetermined position including its orientation, a condition of the electronic part in which it is attracted by a vacuum attracting nozzle must be identified. As for the latter identification, for example, for an IC device, if the IC device is not in an intended attracted position or orientation, then leads of the IC device cannot be placed regularly on lands of the printed circuit board. Therefore, an attracted condition of the IC device is identified, and the position and/or orientation of the IC device are adjusted to mount the IC device onto the printed circuit board.
Referring to FIG. 6A, identification of a position of a printed circuit board is illustratively shown. An electronic part mounting apparatus for mounting an electronic part includes a head in which an attracting nozzle 7 for attracting an electronic part thereto by vacuum is provided. An electronic part attracting section 8 on which the attracting nozzle 7 is supported, a camera 60 and a lens 62 having a fixed magification are also provided in the head of the electronic part mounting apparatus. The head is moved to a position above a printed circuit board 1 placed at a fixed location of the electronic part mounting apparatus, and a reference position of the printed circuit board 1 is inputted to a signal processing apparatus not shown by way of the camera 60 through the fixed magnification lens 62. Such input data are picture processed by the signal processing apparatus to detect an accurate position of the printed circuit board at which an electronic part is to be mounted. Further, referring to FIG. 6B, at a fixed position at which another camera 64 and another fixed magnification lens 66 are disposed, an attracted condition of an electronic part 3 in which it is attracted to the attracting nozzle 7 is inputted to the signal processing apparatus by way of the camera 64 through the fixed magnification lens 66 and then picture processed to identify such attracted condition of the electronic part 3. While such identification of a position of a printed circuit board as illustrated in FIG. 6A is performed once, such identification of an attracted condition of an electronic part as illustrated in FIG. 6B is performed a plurality of times for individual electronic parts.
Referring now to FIG. 7, there is illustrated a route of movement of the head to which an electronic part is attracted. The movable head on which the attracting nozzle 7, electronic part attracting section 8, camera 60 and lens 62 are carried is first moved to a part attracting position CP, at which an electronic part 3 is attracted to the attracting nozzle 7 by vacuum. Then, the head is moved to a picture image processing position IP for which the camera 64 is disposed. Then, an attracted condition of the electronic part 3 is identified from below as illustrated in FIG. 6B. Afterwards, the movable head is moved to a part mounting position MP for a printed circuit board, and then the electronic part 3 is released from vacuum attraction to the attracting nozzle 7 and mounted at a predetermined position of the printed circuit board.
The camera 64 and fixed magnification lens 66 shown in FIG. 6B will be described more in detail. Referring now to FIG. 8, in order to assure accurate identification in accordance with a size of an electronic part to be identified, preferably three fixed magnification lenses 81 to 83 having different fixed magnifications are disposed in front of cameras 85 to 87, respectively, and an attracted condition of an electronic part 8 is inputted by way of the cameras 85 to 87 through half mirrors 71 to 73. Thus, most appropriate video data in connection with the magnifications of the fixed magnification lenses 81 to 83 are used to identify the attracted condition of the electronic part.
Since the camera 64 for identifying an attracted condition of an electronic part is disposed at the picture image processing position IP as shown in FIGS. 6B and 7, the movable head is moved, for each electronic part attracting and mounting operation, along the route including the part attracting postion CP, picture image processing position IP and part mounting position MP. Accordingly, the movable head moves over a comparatively long distance since it moves from and to the picture image processing position IP outside a portion of the route of movement of the head between the other two positions CP and MP. Besides, since accurate positioning at the picture image processing IP is required, a comparatively long time is required for attracting and mounting of an electronic part, and accordingly, the working efficiency is low.
Further, the camera 64 and fixed magnification lens 66 disposed at the fixed position for identifying an electronic part from below as illustrated in FIG. 6B must be provided in addition to the camera 60 and fixed magnification lens 62 carried on the movable head for identifying a printed circuit board from above as illustrated in FIG. 6A, which requires a correspondingly high cost of equipment. Further, while the signal processing apparatus is used commonly for the cameras 60 and 64 disposed at a next stage, common signal processing accuracy cannot be achieved due to a small difference in accuracy between the camera 60 and fixed magnification lens 66 and the camera 64 and fixed magnification lens 66, and besides an operation for adjusting or eliminating such difference is required.
Further, if a plurality of systems of such half mirrors 71 to 73, fixed magnification lenses 81 to 83 and cameras 85 to 87 as shown in FIG. 8 are provided in order to obtain an optimum picture image, then a corresponding high cost of equipment is required, and besides an installation spacing for them may restrict installation of some other parts or may limit movement of the head.